Liquid Crystal Display Device

ABSTRACT

An object of the present invention is to provide a transflective liquid crystal display device having an excellent visibility obtained by optimizing the arrangement of a color filter, which would become a problem in the process of fabricating transparent and reflective liquid crystal display devices, for the transflective liquid crystal display device. In the present invention, the arrangement of a color filter is optimized for improving the visibility of the transflective liquid crystal display device. In addition, the structure, which allows the formation of color filters without increasing the capacitance that affects on a display, is fabricated. Furthermore, in the process of fabricating the transflective liquid crystal display device, an uneven structure is additionally formed without particularly increasing an additional patterning step for the formation of such an uneven structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/575,680, filed Oct. 8, 2009, now allowed, which is a divisional ofU.S. application Ser. No. 10/375,030, filed Feb. 28, 2003, now U.S. Pat.No. 7,612,849, which claims the benefit of a foreign priorityapplication filed in Japan as Serial No. 2002-055874 on Mar. 1, 2002,all of which are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a passive- or active-matrix liquidcrystal display device. Particularly, the present invention relates toan electrode structure of a transflective liquid crystal display devicethat possesses functional properties of both transparent and reflectiveliquid crystal display devices.

2. Description of the Related Art

In recent years, displays adaptable to changes in their useenvironments, power savings, and weight reductions have been desired forthe explosive spread of handheld terminals, typified by cellular phones.

From the viewpoints of achieving the reduction in thickness and weight,a liquid crystal display (LCD) device or an organic electroluminescent(EL) display device may be of typically promising in the art.

A transparent liquid crystal display (LCD) device features its low powerconsumption only for actuating its display device. In this case,however, the liquid crystal itself does not emit light. Therefore, theliquid crystal needs backlighting when it is used in such a displaydevice for providing information or graphics thereon. In uses forcellular phones, electroluminescent (EL) backlights are generallyprovided. However, such an EL backlight requires an additional amount ofelectric power. Therefore, it is difficult to take advantage of thecharacteristic power saving of the liquid crystal in a sufficientmanner, so that the EL backlight has a disadvantage for a reduction inpower consumption. Under the dark environment, a good contrast displaycan be viewed on the screen of the display device. Under the normallighting environment, however, such a display cannot be viewedsufficiently. Therefore, the adaptability to different use environmentsis insufficient in case of either an upper output system or a loweroutput system.

Furthermore, the organic EL display device is characterized in that adisplay element itself emits light. The power consumption of the organicEL display device is higher than that of the reflective liquid crystaldisplay device but smaller than that of the transparent liquid crystaldevice (with backlighting). Just as in the case of the transparentliquid crystal display device, a display can be viewed clearly on thescreen of the display device under the dark environment. Under thenormal lighting environment, however, such a display cannot be viewedsufficiently. Therefore, the adaptability to different use environmentsis insufficient in case of either the upper output system or the loweroutput system.

Furthermore, the reflective liquid crystal display device utilizesoutside light from the environment as light for display. Therefore,principally, there is no need of backlighting on the display's side. Inother words, power is only required for driving the liquid crystal andthe driving circuit. Therefore, power saving can be positively attained.However, as opposed to the former display devices, a display can beclearly viewed under the lighting environment, but it cannot be clearlyviewed under the dark environment. Considering the uses of the handheldterminals, they are mainly used outdoor and displays on their screensmay be viewed under comparatively bright environments in most cases. Inthis case, however, the adaptability to different use environments isstill insufficient. Therefore, front-lighting devices are installed insome of the commercially available handheld terminals such that they canbe provided as reflective display devices capable of providing displaysunder the dark environments.

Consequently, attention is being given to transflective liquid crystaldisplay device because it is constructed as a combination of transparentand reflective liquid crystal display devices so as to have theiradvantageous features, Under the lighting environment, the transflectiveliquid crystal display device utilizes the power-saving property and thegood visibility of the reflective type, while under the darkenvironment, it utilizes the good-contrasting property of thetransparent type using the backlight.

The transflective liquid crystal display device is disclosed in JapanesePatent Laid-Open No. Het 11-101992. In this document, there is discloseda dual-use type (transflective type) reflective transparent liquidcrystal display device integrated with a reflective part by whichoutside light is reflected and a transparent part through which lightfrom the backlighting is transmitted on a single display pixel. When thedevice is in total darkness, it is functioned as a dual-use type liquidcrystal display device where a display is viewed on the screen usinglight emitted from the backlighting and passed through the transparentpart and light reflected from the reflective part formed by a filmhaving a comparatively high reflectivity. When the device is welllighted with outside light, it is functioned as a reflective type liquidcrystal display device where a display is viewed on the screen usinglight reflected from the reflective part formed by a film having acomparatively high reflectivity.

Furthermore, in the transflective liquid crystal display device, aspecific uneven structure (e.g., projections and depressions) having alight-diffusing property is provided particularly on a reflective partthat allows a reflective display on the screen. In the case of thereflecting electrode, because of the structural design thereof, thelight incident on the surface of the reflecting electrode at a certainincident angle in a certain direction is confined such that the lightcan be only reflected from the electrode at a specific output angle in aspecific direction (Snell's law). Therefore, the angle and direction ofthe output light is specifically defined with respect to those of theincident light when the surface of the reflecting electrode is flat. Anydisplay device being produced under such conditions shows a display withan extremely poor visibility.

In the transparent and reflective liquid crystal display devices,furthermore, the placement of color filter is one of causes of parallaxand blurred image.

For example, in the case of a transparent liquid crystal display panelas shown in FIG. 16A, it generally includes a first substrate (an devicesubstrate) 1601 having a first electrode (a transparent electrode) 1602provided as a pixel electrode, a second substrate (a counter substrate)1603 having a second electrode (a transparent electrode) 1606 providedas a counter electrode, and a liquid crystal layer 1607, wherein a blackmatrixes (BMs) (1) 1604 and color filters 1605 are formed between thesecond substrate (the counter substrate) 1603 and the second electrode(the transparent electrode) 1606.

For attaining a higher resolution, compared with one shown in FIG. 16A,an alternative configuration of the LCD panel may be provided as shownin FIG. 16B.

In the transparent LCD panel, the BMs are assembled typically for hidingan escape of light caused by irregularities in the orientation of liquidcrystal at the time of driving the liquid crystal. In the case offorming the BMs and the color filters on the side of the countersubstrate, in general, the dimensions of the BM are defined so as to beslightly larger than the predetermined dimensions thereof withinpredetermined ranges as margins on the assumption that the devicesubstrate and the counter substrate would be deviated within apredetermined range during the step of combining these substratestogether in the process of forming liquid-crystal display devices.

Therefore, in the high-precision panel as shown in FIG. 16B, an openingportion (an opening portion (2)) is sacrificed to ensure the abovemargin (BM margin (2)), so that it would lead to a serious decrease innumerical aperture.

Therefore, as a method for solving the problem of a decrease innumerical aperture accompanied by an increase in resolution, it isconsidered to form color filters 1623 on the first substrate (the devicesubstrate) 1621 as shown in FIG. 16C.

In the case of showing in FIG. 16C, there is no need to provide the BMs(3) with margins against the error of lamination, so that an openingportion (3) can be obtained without sacrificing the numerical aperture.

On the contrary, as shown in FIG. 17A, the configuration of thereflective liquid crystal display device publicly known in the artincludes a first substrate (a device substrate) 1701 having a firstelectrode (a reflective electrode) 1702 provided as a pixel electrode; asecond substrate (a counter substrate) 1703 having a second electrode (atransparent electrode) 1706 provided as a counter electrode, and aliquid crystal layer 1707, wherein black matrixes (BMs) (4) 1704 andcolor filter 1705 are formed between the second substrate (the countersubstrate) 1703 and the second electrode (the transparent electrode)1706. In this case, furthermore, the BMs (4) have the margins inconsideration of an escape of light and the error of lamination betweenthe first substrate (the device substrate) 1701 and the second substrate(the counter substrate) 1703, so that the dimensions of an openingportion can be restricted with the BM margins (4). In other words, thedimension of the opening portion can be represented as an openingportion (4) in the figure.

In this case, regarding the light (1) as shown in FIG. 17A, incidentlight and output light pass through the color filter formed on the samepixel. Regarding the light (2) and (3), on the other hand, incidentlight and output light pass through the color filters formed on thedifferent pixels. In other words, the possibility of which the lightpasses through the color filters formed on the different pixelsincreases when the color filters are formed on the side of the countersubstrate. In some cases, a problem of causing blurred images may arise.

Therefore, for solving such a problem of causing blurred images, asshown in FIG. 17B, a method of forming color filters 1714 on the firstsubstrate (the device substrate) 1711 would be appropriate.

In FIG. 17B, there is illustrated a favorable method for preventing thegeneration of blurred images. In this case, an opening portion (riotshown) can be formed without sacrificing the numerical aperture becauseof no need to provide the BMs (5) with margins to the error oflamination. Also, the ratio of which the incident light and the outputlight pass through the color filter formed on the same pixel increases,compared with that of FIG. 17A.

In this case, however, there is another problem of a decrease ineffective applied voltage because of having a laminated structureobtained by laminating the liquid crystal layer 1717 and the colorfilter 1714 together and the color filter 1714 is formed as part of thecapacitance of the pixel.

It may be said that the transflective liquid crystal display device isone that copes with a special usage condition named a handheld terminal.In particular, it is expected that great demand is anticipated by theapplication to cellar phones in future. For ensuring stable demand oraddressing enormous demand, it is clear that there is the need ofincreasing activity of cost reduction.

However, for forming an uneven structure as described above, there isthe need of providing a method in which a reflecting electrode ismounted after forming an uneven structure on a layer to be located belowthe reflecting electrode. In this process, for realizing such aconfiguration, the number of steps increases because of the need ofpatterning for forming the uneven structure. The increase in the numberof the steps will cause disadvantageous situations including a decreasein yielding percentage, an extension of processing time, and costincrease.

Therefore, an object of the present invention is to provide atransflective liquid crystal display device having a reflectiveelectrode with an uneven structure, which is formed without increasingthe number of the steps in the process.

Furthermore, another object of the present invention is to provide atransflective liquid crystal display device having an excellentvisibility by optimizing the arrangement of a color filter, whichbecomes controversial when the transparent or reflective liquid crystaldisplay device is fabricated, for the transflective liquid crystaldisplay device.

SUMMARY OF THE INVENTION

According to the present invention, for solving the above disadvantages,there is provided an uneven structure, which is additionally formedwithout particularly increasing an additional patterning step for theformation of such a uneven structure in the process of fabricating atransflective liquid crystal display device.

According to the present invention, furthermore. there is provided astructure not only for optimizing the arrangement of a color filter toimprove an excellent visibility of a transflective liquid crystaldisplay device, but also for forming the color filter without increasingits capacitance that affects on a display.

An aspect of the present invention is to provide a liquid crystaldisplay device comprising a plurality of island patterns formed on aninsulating surface, a color filter formed on a plurality of islandpatterns, and a transparent conductive film formed on the color filter.

In the above configuration of the device, a plurality of island patternsmay be formed by etching a reflective conductive film formed on theinsulating surface. Furthermore, a plurality of island patterns areformed from the reflective conductive film, so that the plurality ofisland patterns have a function of reflecting the incident light.

In the present invention, the color filter may be formed so as to besandwiched between a plurality of island patterns and a transparentelectrode made of the transparent conductive film. Therefore, it ispossible to prevent a positional displacement at the time of displayinglight passing through the color filter by the desired pixels, comparedwith the conventional liquid crystal display shown in FIG. 17, either inthe case of reflective display by a plurality of island patterns or inthe case of the display by a transparent electrode.

In the transflective liquid crystal device of the present invention,when a plurality of island patterns and the transparent electrode areformed on a position where they are overlapped through the color filter,light can be reflected on a plurality of island patterns. On the otherhand, when a plurality of island patterns are formed on a position whereit cannot be overlapped with the transparent electrode through the colorfilter, light passes through the transparent electrode.

Consequently, the structure of the present invention has two types ofcharacteristics, reflectivity and transparency. In addition, it also hasan ability of forming an uneven structure on a portion having areflectivity.

In addition, the reflective conductive film may be a conductive filmhaving a reflectivity of 75% or more with respect to a verticalreflection property at a wavelength of 400 to 800 nm (in the visibleregion).

Another aspect of the present invention is to provide a liquid crystaldisplay device comprising a thin film transistor formed on a substrate,a wiring and a plurality of island patterns, prepared by etching thereflective conductive film, which are formed on the thin film transistorthrough an insulating film, a color filter formed on a plurality ofisland patterns, and a transparent conductive film formed on the colorfilter, wherein the wiring establishes an electrical connection betweenthe thin film transistor and the transparent conductive film.

In each of the above configurations, when a plurality of island patternsmade of the reflective conductive film and the wiring are simultaneouslyetched together, the number of steps in the process of photolithographyto be generally used for the formation of an uneven structure can bereduced. Therefore, an extensive cost reduction and an increase inyields can be attained.

Furthermore, the formation and arrangement of a plurality of islandpatterns are performed in a random fashion. However, it is preferablethat the island pattern formed by etching the reflective conductive filmmay be processed such that a taper angle of an end portion of thepattern is more decreased to improve the function of reflection.

In the pixel portion, a percentage of an area occupied by a plurality ofisland patterns made of the transparent conductive film may be 50 to 90%of an area occupied by the pixel portion.

In addition, the transparent electrode formed on the color filter may beformed so as to be connected to the previously formed wiring.

Another aspect of the present invention is to provide a liquid crystaldisplay device comprising a first substrate, a wiring and a plurality ofisland patterns prepared by etching a reflective conductive film formedon an insulating surface over the first substrate, a color filter formedon the plurality of land patterns, a first transparent conductive filmformed on the color filter, a second substrate having a secondtransparent conductive film, and a liquid crystal, wherein the firsttransparent conductive film and the wiring are electrically connected toeach other, a film-formed surface of the first substrate and afilm-formed surface of the second surface face to each other, and theliquid crystal is sandwiched between the first substrate and the secondsubstrate.

Furthermore, still another aspect of the present invention is to providea liquid crystal display device, comprising, a first substrate, a thinfilm transistor formed on the first substrate, a wiring and a pluralityof island patterns prepared by etching a reflective conductive film,which are formed over the thin film transistor through an insulatingfilm, a color filter formed over the plurality of island patterns, afirst transparent conductive film formed on the color filter, a secondsubstrate having a second transparent conductive film, and a liquidcrystal, wherein the wiring establishes an electrical connection betweenthe thin film transistor and the first transparent conductive film, afilm-formed surface of the first substrate and a film-formed surface ofthe second surface face to each other, and the liquid crystal issandwiched between the first substrate and the second substrate.

According to the present invention, the color filter is formed on theisland patterns formed by etching the reflective conductive film formedover the first substrate, and the liquid crystal is formed so as to besandwiched between the first substrate having the transparent conductivefilm formed over the color filter and the second substrate having acounter electrode, with directing their film-formed surfaces inside.Thus, there is provided a structure where the transparent electrode issandwiched between the color filter made of an insulating material andthe liquid crystal, so that the formation of capacitance by the colorfilter can be decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for illustrating a device structure of a liquidcrystal display device in accordance with the present invention.

FIGS. 2A to 20 axe diagrams for illustrating the structure of reflectorsin accordance with the present invention.

FIGS. 3A to 3D are diagrams for illustrating the steps in the process offabricating a liquid crystal display device of the present invention.

FIG. 4 is a diagram for illustrating a process of fabricating a liquidcrystal display device of the present invention.

FIG. 5 is a diagram for illustrating a process of fabricating a liquidcrystal display device of the present invention.

FIG. 6 is a diagram for illustrating a process of fabricating a liquidcrystal display device of the present invention.

FIG. 7 is a diagram for illustrating a process of fabricating a liquidcrystal display device of the present invention.

FIGS. 8A to 8D are diagrams for illustrating the steps in the process offabricating a liquid crystal display device of the present invention.

FIG. 9 is a diagram for illustrating a process of fabricating a liquidcrystal display device of the present invention.

FIG. 10 is a diagram for illustrating a process of fabricating a liquidcrystal display device of the present invention.

FIG. 11 is a diagram for illustrating a structure of a liquid crystaldisplay device of the present invention.

FIG. 12 is a diagram for illustrating a circuit configuration usable inthe present invention.

FIG. 13 is a diagram for illustrating a circuit configuration usable inthe present invention.

FIG. 14 is a diagram for illustrating an external view of a liquidcrystal display device of the present invention.

FIGS. 15A to 15F are diagrams for illustrating examples of an electricdevices;

FIGS. 16A to 16C are diagrams for illustrating a related art.

FIGS. 17A and 17B are diagrams for illustrating a related art.

DETAILED DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will be described withreference to FIG. 1. A semiconductor layer 105 is formed on a substrate101. The semiconductor layer 105 is formed using a polycrystalsemiconductor layer which is prepared by crystallizing an amorphoussemiconductor layer by a heat treatment. In this embodiment, thesemiconductor layer 105 is formed as one having a thickness of about 30to 750 nm, Furthermore, a gate insulating film 106 is formed on thesemiconductor layer 105. Here, the gate-insulating film 106 is formedfrom a silicon oxide layer having a thickness of 30 to 100 nm.

Furthermore, a gate electrode 107 and a capacitor wiring 108 are formedfrom the same layer on the gate insulating film 106. In addition, afirst insulating film 109 including a silicon oxide film and a secondinsulating film 110 including an acryl film are further formed over thegate insulating film 106. Silicon-containing inorganic materials such asa silicon nitride film, a silicon-nitride-oxide film, and a coatingsilicon oxide film (SOG: Spin On Glass) can be used as materials to beformed as the first insulating film 109 instead of the silicon oxidefilm. In addition, organic materials such as polyimide, polyamide, andBCB (benzocyclobutene) can be used as the second insulating film 110instead of the acryl film (including photosensitive acryl).

The wiring 112 is an electrode that makes a contact with a source region102 of a thin film transistor (TFT) 117, which is also a source wiring.In addition, the wiring 113 is an electrode that makes a contact with adrain region 103 of the TFT 117.

In the semiconductor layer 105, the source region 102, the drain region103, and a channel-forming region 104 are formed. In addition, thesemiconductor layer 105 formed in the position overlapped with thecapacitance 108, except the source region 102 and the drain region 103,functions as one electrode of the capacitance element.

Furthermore, reflectors 114 of a plurality of island patterns are formedfrom the same film as a conductive film which forms the wirings 112,113. In other words, the reflectors 114 have a structure like islandsbeing formed with irregular shapes and arrangement so as to have afunction of scattering light incident on the surfaces of the reflectors114.

Furthermore, the reflectors formed in the present invention haveirregular shaped island patterns and the island patterns thereof areirregularly positioned as shown in FIG. 2A in order to scatter light byshifting angle of light incident on the reflectors 204(an incidentangle) from an angle of light reflected from the reflectors (reflectiveangle).

In the present invention, furthermore, a matter of importance for theshift of the incident angle and the reflective angle is the shape ofeach island pattern of the reflectors constituting the reflectiveelectrode. In FIG. 2B, the angle which shows how much a tapere-slopesurface (a reflective surface) 210 of each refrector island is inclinedwith respect to the surface of the substrate (a standard surface) 211.Here, such an angle is defined as a taper angle (θ) 212.

In this embodiment, the reflector is formed such that the taper angle(θ) 212 is included in the range of 5 to 60°. Therefore, it is possibleto improve the visibility of the panel by scattering light with siftingan output angle with respect to the taper-slope surface (the reflectivesurface) 210 of the taper from an output angle with respect to thesurface of the substrate (the standard surface) 211.

FIG. 2C shows behaviors of the incident light 213 and the reflectivelight 214 with respect to the reflective surface without slope,respectively. In the figure, “a_(in)” denotes an incident direction withrespect to the standard surface 211, “a_(out)” denotes an outputdirection with respect to the standard surface 211, “a′_(in)” denotes anincident direction with respect to the reflective surface 210, and“a′_(out)” denotes an output direction with respect to the reflectivesurface 210. In addition, the incident angle (θ₁) 215 and the outputangle (θ₂) 216 are defined with respect to the standard surface. Here,the standard surface 211 and the reflective face 210 are consistent witheach other, so that the equations a_(in)=a′_(in)=θ₁ anda_(out)=a′_(out)=θ₂ are established.

Also, Snell's law gives a′_(in)=a′_(out), so that a_(in)=a_(out) andθ₁=θ₂ are established.

On the other hand, FIG. 2D shows the behaviors of the incident light 213and the output light 214, respectively, when the tapered surface,inclined at a taper angle (θ) 212 is provided as a reflective surface.

The incident light 213 and the output light 214 with respect to thestandard surface 211 are given by and a_(out)=Φ₂′, or a′_(in)=Φ₁′+θ anda′_(out)=Φ₂′−θ, wherein Φ₁′ denotes an incident angle 217 and Φ₂′denotes an output angle 218.

In addition, Snell's law gives a′_(in)=a′_(out), so that the equation:Φ₁′+θ=Φ₂′−θ is given. From the equation, the relationship between theincident angle (Φ₁′) 217 and the output angle (Φ₂′) 218 can be definedas Φ₂′−Φ₁′=2θ. It means that the incident direction (a_(in)) of theincident light 213 and the output direction (a_(out)) of the outputlight 214 are shifted from each other by the degree of 2θ.

For fabricating a panel having an excellent visibility, it is preferablethat the shift angle (2θ) may be uniformly distributed in the range of40° or less. Therefore, it is further preferable that the reflectors 204may be formed so as to have a tapered angle (θ) 212 of 20° or less.

In the present embodiment, the taper angle (θ) 212 of the reflectors 204(114 in FIG. 1) is defined in the range of 5 to 60°, so that lightincident on the reflectors 204 can be efficiently scattered. Therefore,the structure of the present invention is capable of improving thevisibility of a display without increasing the number of steps in theprocess of fabricating the TFT.

Next, as shown in FIG. 1, a color filter 115 is formed on reflectors114, and a transparent electrode 116 is then formed on the color filter115. Furthermore, the transparent electrode 116 is an electrode forallowing the incident light to pass through the electrode 116 toward theside of substrate 101. As a material to be used for preparing thetransparent electrode 116, a transparent conductive film of 100 to 200nm in film thickness, which is prepared of an indium tin oxide (ITO)film or an indium oxide film with 2 to 20% of zinc oxide (ZnO), may beprovided. Such a transparent conductive film is further subjected to thestep of patterning to form the transparent electrode 116 for each pixel.

In the structure of the present invention, the light incident on thereflectors 114 after passing through the transparent electrode 116 isscattered depending on the shapes of the reflectors 114. On the otherhand, the light incident into the space between adjacent reflectors 114without incident on the surface of the reflectors 114 is emitted towardthe substrate 101.

Therefore, the structure of the present invention is capable of formingthe reflectors for scattering light without increasing the number ofsteps in the process of fabricating TFT, thus improving the visibilityof a display. In addition, the structure of the present invention isalso capable of solving the problem of positional sift caused by thearrangement of a color filter, which arises in both the transparent andreflective liquid crystal displays, and also preventing an increase incapacitance to be caused by the arrangement of a color filter.

Furthermore, as explained in the above embodiment of the presentinvention, a transflective liquid crystal display device can befabricated by combining a device substrate (FIG. 1) having TFTs thereonand a counter substrate (not shown) having a counter electrode thereontogether, while placing liquid crystal between these substrate.

EXAMPLES

Hereinafter, we will, describe examples of the present invention.

Example 1

In this example, there is shown an exemplified method for fabricating anactive matrix substrate having a top-gate type thin film transistor(TFT). Here, the example will be described with reference to FIGS. 3A to7, which are top or cross-sectional views of a part of a pixel portion

At first, an amorphous semiconductor layer is formed on a substrate 301having an insulating surface. Here, a quartz substrate is used as thesubstrate 301, and an amorphous semiconductor layer with a filmthickness of 10 to 100 nm is formed on the substrate 301.

Furthermore, the substrate 301 is not limited to the quartz substrate.Alternatively, the substrate 301 may be prepared using a glass substrateor a plastic substrate. In the case of using the glass substrate, it ispreferable that the glass substrate is subjected to a heat treatment inadvance at a temperature about 10 to 20° C. lower than the strain pointof the glass substrate. In addition, a base film may be preferablyformed on the surface of the substrate 301 on which TFT is to be formed.The base film may be including an insulating film such as a siliconoxide film, a silicon nitride film, or a silicon oxynitride film toprevent impurities from diffusing into the substrate 301.

As the amorphous semiconductor layer, an amorphous silicon film of 60 nmin film thickness is formed using a low pressure chemical vapordeposition (LPCVD) method. Then, the amorphous silicon semiconductorlayer is crystallized. In this example, the crystallization is performedusing a technology described in Japanese Patent Laid-Open No. Hei8-78329. The technology described in this patent applicationpublication, a metal element that facilitates the crystallization isselectively added in the amorphous silicon film, followed by subjectingthe amorphous semiconductor film to a heat treatment to form acrystalline silicon film that spreads from the area being added with theabove metal element as a starting point. Here, nickel is used as themetal element that facilitates the crystallization. A heat treatment forthe crystallization (600° C. for 12 hours) is performed after a heattreatment for dehydrogenation (450° C. for 1 hour), Here, it is notedthat the crystallization is not limited to one disclosed in the abovepatent application publication. Alternatively, any crystallizationmethod publicly known in the art may be used (e.g., a lasercrystallization or a thermal crystallization).

If required, laser beam (XeCl: wavelength 308 nm) is irradiated toincrease the rate of crystallization for repairing the defects remainedin crystal grains. The laser beam to be used may be excimer laser beamwith a wavelength of 400 nm or less, or the second or third harmonic ofYAG laser. In either case, a pulse laser beam with a repetitivefrequency of about 10 to 1000 Hz may be used. The laser beam may beconverged through an optical system at a density of 100 to 400 mJ/cm².Subsequently, the laser beam may be irradiated with an overlap rate of90 to 95% for scanning over the surface of the silicon film.

Next, gettering Ni is performed in the area provided as an active layerof TFT. In the following description, an example of using asemiconductor layer containing a rare gas element for gettering. Inaddition to the oxide film formed by the irradiation of laser beam, abarrier layer formed from a oxide film with a total thickness of 1 to 5nm by treating the surface thereof with ozone water for 120 seconds.Subsequently, an amorphous silicon film containing argon with filmthickness of 150 nm, which will become a gettering site, is formed onthe barrier layer by a sputtering method. In this example, thesputtering for the film formation may be performed under the conditionsof a pressure of 0.3 Pa for film formation, a gas (Ar) flow rate of 50sccm, an electric power of 3 kW, and a substrate temperature of 150° C.By the way, in the amorphous silicon film under the above conditions, anatomic percentage of argon is in the range of 3×10²⁰ to 6×10²⁰ atom/cm³,an atomic percentage of oxygen is in the range of 1×10¹⁹ to 3×10¹⁹atom/cm³. After that, the gettering is performed by a thermal treatmentusing a lamp anneal apparatus at 650° C. for 3 minutes. Alternatively,an electric furnace may be used instead of the lamp anneal apparatus.

Next, the barrier layer is used as an etching stopper to selectivelyremove the amorphous silicon film containing Ar of the gettering site,followed by selectively removing the barrier layer with a dilutehydrofluoric acid treatment. Here, nickel (Ni) atoms tend to move to theoxygen-rich area at the time of getter so that it is preferable toremove the barrier layer made of the oxide film.

A thin oxide film is formed on the surface of the silicon film havingthe obtained crystalline structure (also referred to as a polysiliconfilm) by the application of ozone water. After that, a mask made of arest is formed on the above film, followed by subjecting the siliconfilm to an etching treatment to form a semiconductor layers 305 formedfrom a plurality of separated islands with desired patterns. Then, themask is removed after completing the semiconductor layer 305.Subsequently, a gate insulating film 306 of 100 nm in thickness isformed over the surface of the semiconductor layer 305, followed bythermal oxidation.

Furthermore, the step of channel-doping is performed allover orselectively, by which a small amount of p type or n type impurityelement is doped in an area to be provided as a channel-forming regionof TFT. Such a channel-doping is a step for controlling a thresholdvoltage of TFT. Here, it is known that the impurity elements capable ofmaking the semiconductor into p-type are those found in Group 13 of theperiodic table, such as boron (B), aluminum (Al), and gallium (G), whilethe impurity elements capable of making the semiconductor into n-typeare those found in Group 15 of the periodic table, typically phosphorus(P) and arsenic (As). In this example, boron is doped by means of anion-doping method with a plasma excitation of diboran (B₂H₆) withoutmass separation. Alternatively, it may be doped by means of an ionimplantation method with mass separation.

Subsequently, a first conductive film is formed and is then patterned tomake a gate electrode 307 and a capacitor wiring 308 thereon. Here, alaminate structure including tantalum nitride (TaN) (30 nm in thickness)and tungsten (W) (370 nm in thickness) is used. In this example,furthermore, the TFTS are provided with a double gate structure.Besides, the holding capacitor is constituted of the capacitor wiring308 and a region “a” (305 a), which is a part of the semiconductor layer305, using the gate insulating film 306 as a dielectric.

Then, a low concentration of phosphorus is added to a desired region ina self alignment manner using the gate electrode 307 and thecapacitiance wiring 308 as a mask. In this case, the concentration ofphosphorus added in the region is adjusted within the range of 1×10¹⁶ to5×10¹⁸ atom/cm³, typically 3×10¹⁷ to 3×10¹⁸ atom/cm³.

Subsequently, a mask (not shown) is formed and a high concentration ofphosphorus is doped to form impurity regions with a high concentrationto be provided as a source region 302 and a drain region 303,respectively, while adjusting the concentrations of phosphorus in therespective impurity regions with a high concentration within the rangeof 1×10²⁰ to 1×10²¹ atom/cm³ (typically, 2×10²⁰ to 5×10² atom/cm³).Furthermore, a part of the semiconductor layer 305, which is overlappedwith the gate electrode 307, is provided as a channel-forming region304. In addition, another part thereof, which is covered with the mask,is provided as a lightly doped drain (i.e., a LDD region) 311.Furthermore, other areas of the semiconductor area 305, which are notcovered with anyone of the gate electrode 307, the capacitor wiring 308,and the mask, are provided as impurity regions with high concentrationsincluding the source region 302 and the drain region 303.

In this example, TFT of the pixel portion and TFT of the driving circuitare formed on the same substrate. In the TFT of the driving circuit,lightly doped drains may be formed on both sides of the channel-formingregion between the drain region and the source region. In the lightlydoped drains, the concentration of the impurity is smaller than those ofsource and drain regions. However, there is no need to provide thelightly doped drains on the both sides. A manufacturer may appropriatelydesign any mask according to need. For instance, such a lightly dopeddrain may be alternatively formed only one side of the channel-formingregion.

Subsequently, although not shown in the figure, in order to form ap-channel type TFT to be used in the driving circuit formed on the samesubstrate as the pixel, a source region or a drain region is formed bycovering an area to be provided as an n-channel type TFT with a mask anddoping boron (B).

After removing the mask, a first insulating film 309 is formed over thegate electrode 307 and the capacitor wiring 308. Here, a silicon oxidefilm of 50 nm in film thickness is formed and is then subjected to thestep of a thermal treatment to activate n or p type impurity elementbeing doped to the semiconductor layer 305 at each concentrationthereof. In this example, the thermal treatment is carried out at atemperature of 850° C. for 30 minutes (FIG. 3A). Here, the top view ofthe pixel portion is shown in FIG. 4. The cross-sectional profile of thepixel portion along the dotted line A-A′ in FIG. 4 corresponds to thestructure shown in FIG. 3A.

Next, a hydrogenation treatment is performed, followed by forming asecond insulating film 313 made of an organic resin material. In thisexample, the surface of the second insulating film 313 can be flattenedby means of an acryl film of 1 μm in film thickness. An influence ofunevenness caused by the pattern formed on the layer under the secondinsulating film 313 can be prevented. Subsequently, a mask is formed onthe second insulating film 313 to form contact holes 312 extending tothe semiconductor layer 305 (FIG. 3B). After the formation of contactholes 312, the mask is removed. Here, the top view of the pixel portionis shown in FIG. 5. The cross-sectional profile of the pixel portionalong the dotted line A-A′ in FIG. 5 corresponds to the structure shownin FIG. 3B.

Next, a second conductive film is formed and is then pattered to form awiring 315 including a source wiring and a wiring 316 including a drainwiring (concretely, wiring electrically connecting the TFT 310 and atransparent electrode to be formed later) in addition to reflectors 314.The second conductive film being formed here is a reflective conductivefilm to be used for forming the reflectors in the present invention.Preferably, the second conductive film may be prepared using aluminum,silver, or the like, or alloy material mainly comprising these elements.

The second conductive film used in this example is a laminated filmwhich is prepared as a two-layer structure including a Ti film of 50 nmin thickness and a aluminum film of 500 nm in thickness containing Sibeing sequentially deposited by a spattering method.

Here, the patterning is performed using a photolithography to formreflectors 314 having a plurality of island patterns and wirings 315 and316. In addition, the etching method used herein is dry etching toperform taper-etching and anisotropic-etching.

At first, a resist mask is formed, and then a fist etching treatment isperformed for the taper-etching. In the first etching treatment, thefirst and second etching conditions are applied. Preferably, the etchingitself may be an inductively coupled plasma (ICP) etching method. TheICP etching method allows the film to be shaped into a desired taperedconfiguration by appropriately adjusting the etching conditions (anelectric power to be applied to a coil type electrode, an electric powerto be applied to an electrode on the substrate's side, a temperature ofthe substrate's side, and so on). Here, the etching gas may beappropriately selected from chlorine gases typified by, for example,Cl₂, BCl₃, SiCl₄, and CCl₄ and fluorine gases typified by, for example,CF₄, SF₆, and NF₃. Alternatively, O₂ may be appropriately used.

In the present example, as the fist etching condition, the ICP etchingmethod is used. In this case, BCl₃, Cl₂, and O₂ are used as etchinggases and a gas-flow ratio is 65/10/5 (sccm), pressure is 1.2 Pa, and aRF power of 500 W (13.56 MHz) is applied on the coil type electrode togenerate plasma by which the etching can be performed. In addition, anRF power of 300 W (13.56 MHz) is applied on the substrate's side (on asample stage) to apply a substantially negative self bias current. Thefirst etching condition allows the aluminum film containing Si to beetched to make the end of the first conductive layer into a taper shape.

After that, the etching condition is changed from the first one to thesecond one. Further an etching for about 30 seconds is performed withremaining the mask as it is, under the second etching condition withCF₄, Cl₂, and O₂ as the etching gases, a gas-flow ratio of 25/25/10(sccm), a pressure of 1 Pa, and an RF power of 500 W (13.56 MHz) appliedto the coil type electrode to generate plasma. In addition, an RF powerof 20 W (13.56 MHz) is applied on the substrate's side (on a samplestage) to apply a substantially negative self-bias current. Under thesecond etching condition in which CF₄ and Cl₂ are mixed together, thealuminum film containing Si and the Ti film can be etched at the samedegree.

Consequently, the second conductive film composed of the first andsecond conductive layers is shaped into a tapered configuration by thefirst etching treatment.

For performing the anisotropic etching, furthermore, the second etchingtreatment is performed with remaining the resist mask as it is. Here,BCl₃ and Cl₂ are used as the etching gases, a gas-flow ratio is 80/20.(sccm), pressure is 1 Pa, and an RF power of 300 W (13.56 MHz) isapplied on the coil type electrode to generate plasma, thereby thesecond etching is performed. In addition, an RF power of 50 W (13.56MHz) is applied on the substrate's side (on a sample stage) to apply asubstantially negative self-bias voltage.

Consequently, the resist is removed when the formation of the reflectors314 and the wirings 315, 316 is completed, resulting in the structureshown in FIG. 3C. Here, the top view of the pixel portion is shown inFIG. 6. The cross-sectional profile of the pixel portion along thedotted line A-A′ corresponds to the structure shown in FIG. 3C.

Next, the color filter 317 is formed on the reflectors 314. Theformation of the color filter 317 can be performed using materialspublicly known in the art. In this embodiment, these materials areapplied on the reflectors 314 by means of a spin coating to form thecolor filter with a film thickness of 1 μm, followed by a preliminarycuring on a hot plate at 80° C. for 5 minutes. Then, the substrate isexposed to light by a photolithography using a photo mask. After theexposure, the substrate is dipped into a developing solution and is thenshaken for the development. The developing solution used is an aqueoussolution of 0.2% tetramethylammonium hydroxide. After being dipped forabout 1 minute, the substrate is washed in flowing water. Here, ahigh-pressure jet washing is able to remove the residue of the colorfilter, completely. The color filter, furthermore, is formed on thesource wiring and an effective opening portion of the correspondingpixel. In addition, the color filter is arranged such that it is notplaced on the drain wiring 316 that is responsible for making anelectrical connection between the TFT in the lower layer and the pixelelectrode in the upper layer.

After that, when an excellent formation of the pattern has confirmed,then it is subjected to actual baking in a clean oven at 250° C. for 1hour. It is not shown in the figure, however, the above steps areperformed for three different color filters for the respective colors,red, blue, and green.

Furthermore, after the formation of color filters for three colors, anovercoat material (not shown) may be applied over the color filters.

Next, the transparent conductive film of 120 nm in thickness (in thisexample, an indium tin oxide (ITO) film) is formed on the color filter317 by a sputtering method and is then patterned into a rectangle shapeby a photolithography. Subsequently, after performing a wet-etchingtreatment, it is subjected to a heat treatment in a clean oven at 250°C. for 60 minutes, thereby a transparent electrode 318 is performed(FIG. 3D). Here, the top view of the pixel portion is shown in FIG. 7.The cross-sectional profile of the pixel portion along the dotted lineA-A′ corresponds to the structure shown in FIG. 3D.

As shown in FIG. 7, by the way, transparent electrode 318 is formed overthe reflectors 314 having randomly arranged islands through the colorfilter 317. In an area where the transparent electrode 318 and thereflectors 314 are overlapped, light is reflected on the reflectors 314.In another area where the reflectors 314 is not located, light isemitted toward the substrate 301 without reflecting on the reflectors314.

As described above, therefore, the pixel portion including the n-channeltype TFT having the double gate structure and the holding capacitor, andthe driving circuit including both the n-channel type TFT and thep-channel type TFT, can be formed on the same substrate. In thespecification, such a substrate is referred to as an active matrixsubstrate for the sake of convenience.

It is needles to say that the present example has been described asmerely one of the examples and the present invention is not limited tothe steps of the present example. For example, each conductive film mayincludes one selected from tantalum (Ta), titanium (Ti), molybdenum(Mo), tungsten (W), chromium (Cr), and silicon (Si). Alternatively, theabove film may be an alloy film including a mixture of elements selectedfrom these elements (typically, Mo—W alloy or Mo—Ta alloy). Furthermore,each of the insulating films may be a silicon oxide film, a siliconnitride film, a silicon oxynitride film, or a film including an organicmaterial (e.g., polyimide, acryl, polyamide, polyimideamide, orbenzocyclobutene (BCB))

According to the steps illustrated in the present example, as shown inFIG. 3D, the reflectors 314 and wirings 315, 316 can be simultaneouslyformed together using the wiring-pattern mask. Therefore, the reflectingelectrodes can be divided into a plurality of islands on the insulatingfilm without increasing the number of the photo masks to be required inthe process of fabricating an active matrix substrate. Consequently, inthe process of fabricating a transflective liquid crystal displaydevice, the time required for the steps are reduced to contribute to areduction in manufacturing costs and to an increase in yields.

Example 2

This embodiment concretely explains a method for manufacturing atransflective type liquid crystal display device different in thestructure from that of Embodiment 1 with reference to FIGS. 8A to 10.

At first, an amorphous semiconductor film is formed on a substrate 801as shown in FIG. 8A. After crystallizing this, a semiconductor layer 805is formed which is separated in an island form by patterning.Furthermore, on the semiconductor layer 805, a gate insulating film 806is formed by an insulating film. Incidentally, the manufacturing methodof up to forming the gate insulating film 806 is similar to that shownin example 1, and hence example 1 may be referred to. Similarly, afterforming an insulating film covering the semiconductor layer 805, thermaloxidation is carried out to form a gate insulating film 806.

Then, a channel dope process is carried out over the entirely orselectively, to add a p-type or n-type impurity element at lowconcentration to a region which will become a TFT channel formingregion.

A conductive film is formed on the gate insulating film 806. Bypatterning this, a wiring 809 which will become the electrode 807, acapacitor wiring 808 and a source line can be formed. Incidentally, thefirst conductive film in this embodiment is formed by laminating TaN(tantalum nitride) formed in a thickness of 50 to 100 nm and W(tungsten) formed in a thickness of 100 to 400 nm.

Although the conductive film is formed by the use of the laminated filmof TaN and W in this embodiment, they are not especially limited, i.e.both may include an element selected from Ta, W, Ti, Mo, Al and Cu or analloy or a compound material mainly containing the above elements.Otherwise, a semiconductor film that is represented by a polycrystalsilicon film doped with an impurity element, such as phosphorus may beused.

Then, phosphorus is added at low concentration by use of the gateelectrode 807 and capacitor wiring 808 as masks in a self-alignmentmanner. In the region added at low concentration, phosphorusconcentration is controlled to 1×10¹⁶ to 5×10¹⁸ atom/cm³, typically3×10¹⁷ to 3×10¹⁸ atom/cm³.

Next, a mask (not shown) is formed to add phosphorus at highconcentration to form an impurity region with high concentration whichwill become a source region 802 or drain region 803. In this impurityregion with high concentration, phosphorus concentration is controlledto 1×10²⁰ to 1×10²¹ atom/cm³ (typically 2×10²⁰ to 5×10²⁰ atom/cm³). Thesemiconductor layer 805 in a region overlapped with the gate electrode807 will become a channel-forming region 804. The region covered by themask will become an impurity region with low concentration of LDD region811. Furthermore, the region which is not covered by any of the gateelectrode 807, the capacitor wiring 808 and the mask will become animpurity region with high concentration including a source region 802and a drain region 803.

Meanwhile, because this embodiment forms p-channel TFTs to be used for adriver circuit formed on the same substrate as the pixels similarly toexample 1, the region which will become n-channel TFTs is covered by amask to add boron thereby forming a source or drain region.

Then, after removing the mask, a first insulating film 810 is formedcovering the gate electrode 807, the capacitor wiring 808 and wiring(source line) 809. Herein, a silicon oxide film is formed in a filmthickness of 50 nm, and a thermal process is carried out to activate then-type or p-type impurity element added at respective concentrations inthe semiconductor layer 805. Herein, thermal process is made at 850° C.for 30 minutes (FIG. 8A).

Then, after carrying out a hydrogenation process, a second insulatingfilm 811 is formed of an organic resin material. By herein using anacryl film having a film thickness of 1 μm, the second insulating film811 can be flattened in its surface. This prevents the influence of astep caused by the pattern formed in the layer beneath the secondinsulating film 811. Then, a mask is formed on the second insulatingfilm 811 to form by etching a contact hole 812 reaching thesemiconductor layer 805 (FIG. 8B). After forming the contact hole 812,the mask is removed away.

Next, a second conductive film is formed and patterned. Due to this,formed are, besides a reflection electrodes 814, a wiring 815electrically connecting the wiring (source line) 809 and the sourceregion of TFT 810, a wiring 816 connected electrically with thecapacitor wiring 808, and a wiring 817 electrically connecting the drainregion of TFT 810 and the transparent electrode 819 (In FIG. 8D, theconnecting relation is not illustrated). The second conductive filmformed herein is a reflective conductive film to form the reflectors ofthe invention, which can use aluminum or silver, or otherwise an alloymaterial based on these.

This embodiment uses a laminated film having a two-layer structurecontinuously formed, by sputtering, with a Ti film having 50 nm and anSi-contained aluminum film having 500 nm as the second conductive film.

Photolithography technique is applied for pattering to form reflect 814including a plurality of island-formed patterns and wirings 815, 816,817. Also, a dry etching is applied for etching to carry out taperetching and anisotropic etching.

At first, a resist mask is formed to carry out a first etching processfor taper etching. The first etching process is under first and secondetching conditions. For etching, an ICP (Inductively Coupled Plasma)etching technique is suitably used. Using the ICP etching technique, thefilm can be etched to a desired taper form by properly controlling theetching condition (amount of power applied to a coil type electrode,amount of power applied to the electrode of the substrate side, anelectrode temperature of the substrate side, etc.). A chlorine-based gasrepresented by Cl₂, BCl₃, SiCl₄, CCl₄ or the like, a fluorine-based gasrepresented by CF₄, SF₆, NF₃ or the like, or O₂ are can be suitably usedas the etching gas.

This embodiment uses the ICP (Inductively Coupled Plasma) etchingtechnique, as a first etching condition, wherein BCl₃, Cl₂ and O₂ areused for an etching gas. Etching is conducted with plasma caused byfeeding a 500 W RF (13.56 MHz) power to a coil type electrode at a flowrate ratio of these gasses of 65/10/5 (sccm) under a pressure of 1.2 Pa.A 300W RF,(13.56 MHz) power is fed also to the substrate side (samplestage) to apply substantially a negative self-bias voltage. Under thefirst etching condition, the aluminum film containing Si is etched tomake the first conductive layer at its end into a taper shape.

Thereafter, the etching condition is changed to the second etchingcondition without removing the mask. Using CF₄, Cl₂ and O₂ as etchinggases, etching is conducted for nearly 30 seconds with plasma caused byfeeding a 500 W RF (13.56 MHz) power to the coil type electrode at aflow ate ratio of these gasses of 25/25/10 (sccm) under a pressure of 1Pa. A 20 W RF (13.56 MHz) power is fed also to the substrate side(sample stage) to apply substantially a negative self-bias voltage.Under the second etching condition having CF₄ and Cl₂ mixed together,the aluminum film containing Si and the Ti film are both etched in thesame degree.

In this manner, by the first etching process, the second conductive filmcomprising the first and second conductive layers can be made into ataper shape.

Then, a second etching process for anisotropic etching is carried outwithout removing the resist mask. Using herein BCl₃ and Cl₂ for etchinggases, etching is conducted with plasma caused by feeding a 300 W RF(13.56 MHz) power to the coil type electrode at a flow rate ratio ofthese gasses of 80/20 (seem) under a pressure of 1 Pa. A 50 W RF (13.56MHz) power is fed also to the substrate side (sample stage) to applysubstantially a negative self-bias voltage.

By the above, at a time that reflectors 814 and wirings 815, 816, 817are formed, the resist is removed to obtain a structure shown in FIG.8C. Incidentally, pixel top view herein is shown in FIG. 9. In FIG. 9,the sectional view taken along the dotted line A-A′ corresponds to FIG.8C.

Then, a color filter 818 is formed on the reflectors 814. Publicly knownmaterials can be used as the material for the color filter 818. In thisembodiment, these materials are applied by spin coating to form thecolor filter having 1 μm thickness. Then, preliminary curing isconducted on hot plate at 80° C. for 5 minutes. And then, it is exposedwith photomask to photolithography. After the processing, the substrateis immersed in a developing solution and developed by shaking.Tetramethylammonium hydroxide 0.2% solution is applied for thedeveloping solution. After dipped in the developing solution for about 1minute, the substrate is rinsed under flowing water. The residue of thecolor filter can be completely removed by conductive high-pressure jetwashing. The color filter is only formed over, the effective openingportion of corresponding pixels, except for over the wiring 816connected to the capacitor wiring 808. Though color filter is formed ona part of the wiring 817. However, it is not formed on the connectingportion of wiring 817 and the transparent electrode 819.

When the pattern is formed properly, the substrate is baked in a cleanoven at 250° C. for 1 hour. Not illustrated here, above processing isdone with three color filters, namely, red, blue, and green in thisexample.

After the three color filters are formed, overcoat material (not shown)can be applied thereon.

A transparent conductive film (here, indium tin oxide (ITO) film) isformed with a thickness of 120 nm by sputtering on the color filter 818,and patterned to have rectangular shape by photolithography technique.Then, after wet etching is performed thereon, a transparent electrode819 is formed by conductive heat treatment in a clean oven at 250° C.for 60 minutes (FIG. 8D). A top view thereof is shown in FIG. 10. InFIG. 10, the cross-sectional view taken along the line A-A′ correspondsto FIG. 8D.

Further, as shown in FIG. 10, the transparent electrode 819 is formedover the reflectors 814 formed randomly through the color filter 818.With this construction, light is reflected by the reflectors 814 in theplace where the transparent electrode 819 and the reflectors 814 areoverlapped, and in the potion where the reflectors 814 are not formed,light is not reflected by the reflectors 814 and emitted toward thesubstrate 801.

Accordingly, in this embodiment, the active matrix substrate is formedon which the pixel portion having an n-channel TFT of double gatestructure and a holding capacitor, and the driving circuit having ann-channel TFT and the p-channel TFT are formed on the same substrate.

Meanwhile, according to the process shown in this example, it ispossible to simultaneously form the reflectors 814 and wirings (815,816, 817) by using a wiring pattern mask as shown in FIG. 8D.Consequently, plurality of the reflectors can be formed separately in anisland form without increasing the number of photo-masks required forfabricating the active matrix substrate. As a result, in the manufactureof a transflective liquid crystal display device, the process can beshortened thereby giving contribution to manufacture cost reduction andyield improvement.

Example 3

This embodiment describes a process of manufacturing a liquid crystaldisplay device from the active matrix substrate fabricated in example 1.The description is given with reference to cross-sectional view of FIG.11.

After the active matrix substrate as illustrated in FIG. 3D is obtainedin accordance with example 1, an oriented film 1117 is formed over theactive matrix substrate of FIG. 3D and rubbing treatment is performed.In this example, after the oriented film 1117 is formed, sphericalspacers 1121 are dispersed over the entire surface of the substrate inorder to keep the distance between the substrates. The spherical spacers1121 may be replaced by columnar spacers formed of an organic resin filmsuch as an acrylic resin film patterned in desired portions.

A substrate 1122 is prepared next. On the substrate 1122, a counterelectrode 1123 is formed from a transparent conductive film in theportion where a pixel portion will be formed. An oriented film 1124 isformed over the entire surface of the substrate 1122 and is a rubbingtreatment is performed. Then, a counter substrate 1126 is obtained.

Then, the counter substrate 1126 is bonded to the active matrixsubstrate on which the oriented film 1117 is formed, using a sealingmember (not shown). The sealing member has filler mixed therein and thefiller, together with the columnar spacers, keeps the uniform distancebetween the two substrates (preferably 2.0 to 3.0 μm) while they arebonded. Thereafter a liquid crystal material 1125 is injected betweenthe substrates and a sealant (not shown) is used to completely seal thesubstrates. A publicly known liquid crystal material can be used. Thetransflective liquid crystal display deice-shown in FIG. 11 is thuscompleted. If necessary, the active matrix substrate or the countersubstrate 1126 is cut into pieces of desired shapes. The display devicemay be appropriately provided with a polarizing plate using a publiclyknown technique. Then FPCs are attached to the substrate using apublicly known technique.

The structure of the thus obtained liquid crystal module is describedwith reference to the top view in FIG. 14. A pixel portion 1404 isplaced in the center of an active matrix substrate 1401. A source signalline driving circuit 1402 for driving source signal lines is positionedabove the pixel portion 1404. Gate signal line driving circuits 1403 fordriving gate signal lines are placed to the left and right of the pixelportion 1404. Although the gate signal line driving circuits 1403 aresymmetrical with respect to the pixel portion in this example, theliquid crystal module may have only one gate signal line driving circuiton one side of the pixel portion. Of the above two options, a designercan choose the arrangement that suits better considering the substratesize or the like of the liquid crystal module. However, the symmetricalarrangement of the gate signal line driving circuits shown in FIG. 14 ispreferred in terms of circuit operation reliability, driving efficiency,and the like.

Signals are inputted to the driving circuits from flexible printcircuits (FPC) 1405. The FPCs 1405 are press-fit through an anisotropicconductive film or the like after opening contact holes in theinterlayer insulating film and resin film and forming a connectionelectrode so as to reach the wiring lines arranged in given places ofthe substrate 1401. The connection electrode is formed from ITO in thisexample.

A sealing member 1407 is applied along its periphery around the drivingcircuits and the pixel portion. A counter substrate 1406 is bonded tothe substrate 1401 while a spacer formed in advance on the active matrixsubstrate keeps the distance between the two substrates constant (thedistance between the substrate 1401 and the opposed substrate 1406). Aliquid crystal is injected through an area that is not coated with thesealing member 1407. The substrates are then sealed by a sealant 1408. Aliquid crystal module is completed through the above processing.Although all of the driving circuits are formed on the substrate in theexample shown here, several ICs may be used for some of the drivingcircuits. The active matrix type liquid crystal module is completedthrough the above steps.

Example 4

FIGS. 12, 13 show block diagrams of an electro-optical devicemanufactured in accordance with the present invention. FIG. 12 shows acircuit structure for the device that is driven by analog driving. Thisexample describes an electro-optical device having a source line drivingcircuit 90, a pixel portion 91, and a gate line driving circuit 92. Theterm of driving circuit herein collectively refers to a source linedriving circuit and a gate line driving circuit.

The source line driving circuit 90 is provided with a shift register 90a, a buffer 90 b, and a sampling circuit (transfer gate) 90 c. The gateline driving circuit 92 is provided with a shift register 92 a, a levelshifter 92 b, and a buffer 92 c. If necessary, a level shifter circuitmay be provided between the sampling circuit and the shift register.

In this embodiment, the pixel portion 91 includes a plurality of pixels,and each of the plural pixels has TFT elements.

Though not shown in the drawing, another gate line driving circuit maybe provided in the other side of the gate line driving circuit 92 withthe pixel portion 91 therebetween.

When the device is driven by digital driving, the sampling circuit isreplaced by a latch (A) 93 b and a latch (B) 93 c as shown in FIG. 13. Asource line driving circuit 93 is provided with a shift register 93 a,the latch (A) 93 b, the latch (B) 93 c, a D/A converter 93 d, and abuffer 93 e. A gate line driving circuit 95 is provided with a shiftregister 95 a, a level shifter 95 b, and a buffer 95 c.

If necessary, a level shifter circuit may be provided between the latch(B) 93 c and the D/A converter 93 d.

The above structure is obtained by employing the manufacture process ofany of example 1 or 2. Although this example describes only thestructure of the pixel portion and the driving circuit, a memory circuitand a microprocessor circuit can also be formed when following themanufacture process of the present invention.

Example 5

The transflective liquid crystal display device formed by implementingthe present invention can be used for various electro-optical devices.The present invention can be applied to all electric appliances in whichthe electro-optical device is built as a display medium.

Given as examples of an electric appliance that employs a liquid crystaldisplay device manufactured in accordance with the present invention arevideo cameras, digital cameras, navigation systems, audio reproducingdevices (such as car audio and audio components), laptop computers, gamemachines, portable information terminals (such as mobile computers,cellular phones, portable game machines, and electronic books), andimage reproducing devices equipped with recording media (specifically,devices with a display device that can reproduce data in a recordingmedium such as a digital video disk (DVD) to display an image of thedata). Specific examples of these electric appliance are shown in FIGS.15A to 15H.

FIG. 15A shows a digital still camera, which is composed of a main body2101, a display unit 2102, an image receiving unit 2103, operation keys2104, an external connection port 2105, a shutter 2106, etc. The digitalcamera is completed by using the liquid crystal display devicemanufactured in accordance with the present invention for the displayunit 2102.

FIG. 155 shows a laptop computer, which is composed of a main body 2201,a case 2202, a display unit 2203, keyboard 2204, an external connectionport 2205, a pointing mouse 2206, etc. The laptop computer is completedby using the liquid crystal display device manufactured in accordancewith the present invention for the display unit 2203.

FIG. 15C shows a mobile computer, which is composed of a main body 2301,a display unit 2302, a switch 2303, operation keys 2304, an infraredport 2305, etc. The mobile computer is completed by using the liquidcrystal display device manufactured in accordance with the presentinvention for the display unit 2302.

FIG. 15D shows a portable image reproducing device equipped with arecording medium (a DVD player, to be specific). The device is composedof a main body 2401, a case 2402 a display unit A 2403, a display unit B2404, a recording medium (DVD or the like) reading unit 2405, operationkeys 2406, speaker units 2407, etc. The display unit A 2403 mainlydisplays-image information whereas the display unit B 2404 mainlydisplays text information. The portable image reproducing device iscompleted by using the liquid crystal display device manufactured inaccordance with the present invention for the display units A 2403 and B2404. The image reproducing device equipped with a recording medium alsoincludes home-video game machines.

FIG. 15E shows a video camera, which is composed of a main body 2601, adisplay unit 2602, a case 2603, an external connection port 2604, aremote control receiving unit 2605, an image receiving unit 2606, abattery 2607, an audio input unit 2608, operation keys 2609, eye pieceportion 2610 etc. The video camera is completed by using the liquidcrystal display device manufactured in accordance with the presentinvention for the display unit 2602.

FIG. 15F shows a cellular phone, which is composed of a main body 2701,a case 2702, a display unit 2703, an audio input unit 2704, an audiooutput unit 2705, operation keys 2706, an external connection port 2707,an antenna 2708, etc. The cellular phone is completed by using theliquid crystal display device manufactured in accordance with thepresent invention for the display unit 2703. If the display unit 2703displays white letters on black background, the cellular phone consumesless power.

As described above, the application range of the liquid crystal displaydevice manufactured in accordance with the present invention is so widethat it is applicable to electric appliances of any field. The electricappliances of this example can be completed by using the liquid crystaldisplay device formed by implementing examples 1 to 4.

Accordingly, by implementing the present invention, wirings including areflective conductive film and a plurality of island patterns which willbecome reflectors can be concurrently formed together in the process offabricating a transflective liquid crystal display device. In thepresent invention, furthermore, a transparent electrode formed from atransparent conductive film is formed over the reflectors through acolor filter. Therefore, the reflectors improve the visibility of adisplay without increasing the number of the steps in the fabricatingprocess, and also the arrangement of the color filter can prevent animage from being displaced or blurred without increasing thecapacitance. Consequently, the fabrication of a liquid crystal devicehaving a high quality and a substantial cost-cutting can be attained.

What is claimed is:
 1. A liquid crystal display device comprising: aplurality of reflectors formed over an insulating surface; a colorfilter formed over the plurality of the reflectors; and a transparentconductive film formed over the color filter.